Planar Write Module And Hybrid Planar Write-Vertical Read Bidirectional Tape Head

ABSTRACT

A planar write module and a hybrid planar write-vertical read bidirectional tape head comprising the write module and one or more vertical read modules. The write module has a write module tape bearing surface for engaging the magnetic recording tape. Plural write elements in the write module each comprise plural thin film layers oriented in generally parallel planar relationship with the write module tape bearing surface. The write elements are arranged so that the transducing gaps of adjacent write elements are generally aligned in a direction that is transverse to a streaming direction of the magnetic recording tape. Each read module has a read module tape bearing surface for engaging the magnetic recording tape. Plural read elements in the one or more read modules each comprise plural thin film layers oriented in generally perpendicular relationship with the read module tape bearing surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to tape drive data storage systems. Moreparticularly, the invention is directed to thin film tape heads forreading and writing data on magnetic recording tape.

2. Description of the Prior Art

Thin film tape heads for magnetic information storage systems (e.g.,tape drives) have been constructed using the same fabrication techniquesused by disk drive manufacturers. A characteristic of such constructionis that the thin film layers which comprise the read and writetransducer elements are oriented perpendicularly to the tape bearingsurface (TBS) of the head. Such heads may be referred to as “vertical”heads due to the fact that the read and write gap portions are situatedat the TBS, while the element layer structures extend vertically awayfrom the TBS. In a vertical head with multitrack recording capability,plural transducer elements are commonly arranged side-by-side to form alinear transducer array that is transverse to the direction of tapemovement. Each transducer element in the array is positioned to write orread a separate longitudinal track on the tape. This arrangement isshown in FIG. 1, which depicts a vertical head “H” having an array ofthin film transducer elements “E” whose gaps “G” engage a tape “T” alongtracks “TR” in the direction of tape movement “D.” FIG. 2 illustrates anexemplary internal construction of the vertical head “H” in which thetransducers comprise alternating read and write elements “R” and “W.” Asshown in FIG. 3, the vertical head “H” of FIG. 2 can be secured to amounting block “MB” in association with a complimentary vertical head“H′” whose read and write elements are in reverse order. The resultanthead assembly will have read/write element pairs that are aligned in thetrackwise direction of the tape “T.” This arrangement providesconventional read-after-write capability in which data written to thetape “T” is immediately read back and checked for errors.Read-after-write capability may also be achieved with a single verticalhead having pairs of trackwise-aligned read and write elements that areconstructed according to the well-known “piggyback” arrangement used indisk drives. Other conventional vertical head designs include heads inwhich all of the transducer elements “E” are either read elements orwrite elements. Read-after-write capability may then be achieved bybonding a read-only head to a write-only head to providetrackwise-aligned read and write element pairs.

A disadvantage of vertical head constructions as described above is thatthe transducer element gaps at the TBS must be sufficiently spaced fromeach other to provide room for the major portion of the transducerelement structure that is recessed behind the TBS. For a write element,the recessed structure includes the pole pieces and the coil windings,which (as can be seen in FIG. 2) are quite bulky as compared to thewrite gap structure at the TBS. For a read element, the recessedstructure includes the electrical leads and magnetic hard biasingelements (if present). These are also relatively bulky compared to theread gap structure at the TBS, although less so compared to writeelements. The foregoing spacing requirements render the transducer arrayof a vertical head much wider than it needs to be for the number oftracks being read or written at any given moment. The problem is thatthe gap pitch within the transducer array is much larger than the gapwidth, such that for every track being read or written by the array,there will be space between the tracks where no transducing occurs. This“comb” effect can be seen in FIG. 2, which shows that for every pair oftracks “TR” aligned with adjacent read and write elements “R” and “W,”there is inter-track white space on the tape “T” that is not tranduced.

The comb effect can be solved by stepping the head in a cross-trackdirection during multiple transducing passes, such that the inter-trackwhite space is ultimately recorded with data after some number of passeshave been made. Tape tracks can also be written at less than the gapwidth of the write transducers using a process known as “shingling.”According to this technique, the head is stepped by less than the writeelement gap width for each successive transducing pass, such that theedge of a previously written track is overwritten during the next pass,much like shingles on a roof.

Although the foregoing track writing techniques allow data to be denselypacked on a tape, a continuing unresolved problem is trackmisregistration caused by tape dimensional changes between writing andreading operations. For example, a tape may be written with data underone set of temperature and humidity conditions, and then later readfollowing exposure to different environmental conditions. Forconventional tape material, the dimensions can change by as much as0.12%. These tape dimensional changes will widen or narrow the tapetrack spacing geometry, resulting in track misregistration with the tapehead whose gap spacing geometry is substantially unchanged. Althoughrotation of the tape head can be used to address the misregistrationproblem by changing the effective track pitch of the transducer array,this solution requires sophisticated mechanics and skew compensationcircuitry.

To illustrate the misregistration problem, assume the transducer arrayspans x μm between the outermost elements, and the percentage change intape dimension is 0.12%. The resultant change in the spacing of the tapetracks under the outermost elements will be 0.0012×μm. On the otherhand, if the transducer array spans 0.5×μm, then a 0.12% change in tapedimension will only change the tape track spacing under the outermostelements by 0.0006×μm. The 0.5× transducer array span will thusexperience only half of the tape dimensional change that is experiencedby the x transducer span, such that track misregistration is lesslikely.

Accordingly, it is desired to have an improved design for a thin filmtape head for reading and writing data on magnetic recording tape. Whatis particularly needed is a head design that provides the ability toreduce the gap pitch of read and write elements.

SUMMARY OF THE INVENTION

The foregoing problems are solved and an advance in the art is obtainedby a planar write module and a hybrid planar write-vertical readbidirectional tape head comprising the write module and one or morevertical read modules. The write module has a write module tape bearingsurface for engaging the magnetic recording tape. Plural write elementsin the write module each comprise plural thin film layers oriented ingenerally parallel planar relationship with the write module tapebearing surface. The write elements are arranged so that the transducinggaps of adjacent write elements are generally aligned in a directionthat is transverse to a streaming direction of the magnetic recordingtape. Each read module has a read module tape bearing surface forengaging the magnetic recording tape. Plural read elements in the one ormore read modules each comprise plural thin film layers oriented ingenerally perpendicular relationship with the read module tape bearingsurface.

In one exemplary embodiment disclosed herein, the write elementscomprise a pancake coil construction. In another exemplary embodimentdisclosed herein, the write elements comprise a helical coilconstruction. In both embodiments, the write elements may comprise apair of pole tips providing a write gap at the write module tape bearingsurface and a pair of pole pieces extending from the pole tips to a backgap region where the pole pieces are joined, with the back gap regionbeing spaced in a trackwise direction from the write gap. The writeelements may be arranged in one or more arrays.

Servo read elements may also be formed on the write module, eachcomprising plural thin film layers oriented in parallel planarrelationship with the write module tape bearing surface. A flux guideconstruction may be used to form the servo read elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following more particular description of exemplaryembodiments of the invention, as illustrated in the accompanyingDrawings, in which:

FIG. 1 is a perspective view showing a prior art thin film vertical tapehead;

FIG. 2 is a perspective view showing an exemplary construction of theprior art tape head of FIG. 1;

FIG. 3 is a side elevation view showing a pair of the vertical tapeheads of FIG. 1 secured to a mounting block;

FIG. 4 is a partial plan view showing a tape bearing surface of anexemplary hybrid tape head, with a segment of magnetic recording tapesuperimposed over the tape head;

FIG. 4A is a plan view showing a plural write element array version ofthe hybrid tape head of FIG. 4;

FIG. 5 is an enlarged plan view showing a portion of a write module ofthe tape head of FIG. 4;

FIG. 6 is write element cross-sectional view taken along line 6-6 inFIG. 5;

FIG. 7 is a head cross-sectional view taken along line 7-7 in FIG. 4;

FIG. 8 is a plan view showing an exemplary write module servo reader;

FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 8;

FIG. 10 is a side view taken in the direction of the arrows 10-10 inFIG. 9;

FIG. 11 is a partial plan view showing a tape bearing surface of anotherexemplary hybrid tape head, with a segment of magnetic recording tapesuperimposed over the tape head;

FIG. 11A is a plan view showing a plural write element array version ofthe hybrid tape head of FIG. 11;

FIG. 12 is an enlarged plan view showing a portion of a write module ofthe tape head of FIG. 11;

FIG. 13 is write element cross-sectional view taken along line 13-13 inFIG. 12;

FIG. 14 is a head cross-sectional view taken along line 14-14 in FIG.11;

FIG. 15 is a functional block diagram showing a tape drive data storagedevice; and

FIG. 16 is a perspective view showing an exemplary construction of thetape drive storage device of FIG. 15 for use with cartridge-based tapemedia.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The invention will now be described by way of exemplary embodimentsshown by the drawing figures (which are not necessarily to scale), inwhich like reference numerals indicate like elements in all of theseveral views.

Turning now to FIG. 4, a tape head 2 is constructed according to anexemplary three-module configuration in which a planar write module 4 isdisposed between a pair of vertical read modules 6 and 8. In analternative three-module configuration (not shown), a single one of thevertical read modules 6 or 8 could be disposed between two of the planarwrite modules 4. The write module 4 has a write module tape bearingsurface 10 for engaging a magnetic recording tape “T,” one edge of whichis shown in FIG. 4. As additionally shown in FIGS. 5-7, the write module4 has a planar head construction in which plural write elements 12 inthe write module 4 each comprise plural thin film layers “L” oriented ingenerally parallel planar relationship with the write module tapebearing surface 10. It will be seen that the write elements 12 arearranged so that the transducing gaps 14 of adjacent write elements aregenerally aligned in a direction that is transverse to a streamingdirection of the magnetic recording tape (shown by the arrow “D” in FIG.4). As shown in FIG. 4A, the write elements 12 may be arranged in one ormore arrays. Plural arrays allow more tracks to be written in a singlepass of the write module 4, with reduced track pitch.

Each of the modules 6 and 8 has a read module tape bearing surface 16for engaging the magnetic recording tape “T.” As additionally shown inFIG. 7, the read modules 6 and 8 have a conventional vertical headconstruction in which plural read elements 18 each comprise plural thinfilm layers oriented in generally perpendicular relationship with theread module tape bearing surface 16. Although not shown, adjacent readelements 18 may be formed in different layers of the read modules 6 and8 to reduce read gap spacing requirements. Although the read modules 6and 8 are shown in FIGS. 4 and 7 as being contiguous with the writemodule 4, one or both of the read modules could be spaced from the writemodule in a fixed relationship therewith.

In the exemplary embodiment represented by FIGS. 4-7, the write elements12 comprise a pancake coil construction. According to this construction,the write coil 20 is constructed with plural coil windings in a singleone of the thin film layers “L,” as can be seen in FIG. 6. A pair ofcontact pads 22 and 24 are provided for connecting the write coil 20 toan information-modulated current source (not shown). The write elements12 further comprise a pair of pole tips 26 and 28 that provide the writegap 14 at the write module tape bearing surface 10. A pair of polepieces 30 and 32 respectively extend from the pole tips 26 and 28 to aback gap region 34 where the pole pieces are joined. The pole tips 26/28and the pole pieces 30 and 32 can be formed from any suitablemagnetically permeable material of the type conventionally used tofabricate inductive write heads for information storage. As can be seenin FIG. 6, the pole pieces 30 and 32 initially extend from the pole tips26 and 28 in a direction that is generally perpendicular to the writemodule tape bearing surface 10. Each pole piece 30 and 32 then makes anapproximate 90° bend at a separate one of the layers “L” of the writemodule 4, and thereafter extends generally parallel to the write moduletape bearing surface 10 to the back gap region 34. The back gap region34 is thereby spaced in a trackwise (i.e., along the track) directionfrom the write gap 14.

It will be seen in FIGS. 5 and 6 that the write coil 20 wraps around theback gap region 34 with the coil windings on one side of the back gapregion being disposed between the pole pieces 30 and 33. When the writecoil 20 is energized, it will induce magnetic flux in the pole pieces 30and 32 so as to produce a magnetic field at the pole tips 26 and 28 thatpropagates across the write gap 14. It will be appreciated that thestrength of the magnetic field at the write gap 14 depends in part onthe number of windings of the write coil 20. Although not shown, one wayto increase the number of coil windings without increasing the overallsize of the write elements (when viewed in the plan view orientation ofFIG. 5) would be to form the additional windings on one or more separatelayers “L” of the write module 4.

As shown in FIG. 4, the tape head 2 includes servo read elements forreading conventional timing-based servo tracks “ST” on the tape “T.” Theservo read elements may be provided by additional read elements 18 onthe read modules 6 and 8, or they may be provided by planar servo readelements 36 on the write module 4. As shown in FIGS. 8-10, each planarservo read element 36 comprises a sensor structure 38 formed in pluralthin film layers “L” of the write module 4 that are oriented in parallelplanar relationship with the write module tape bearing surface 10. Aspersons skilled in the art will appreciate, the sensor structure layersmay include a magnetic pinned layer 40, a spacer layer 42 and a magneticfree layer 44. A pair of electrode/hard biasing structures 46 may beprovided on each side of the sensor structure to provide a CIP(Current-In-Plane) sensor. Although not shown, a CPP(Current-Perpendicular to-Plane) sensor could also be used. Aconventional flux guide is used to carry magnetic flux from the writemodule tape bearing surface 10 to the free layer 44.

FIG. 7 shows the tape head 2 when viewed from the edge of the tape “T”of FIG. 4. As can be seen, electrical connections are made to the writeelements 12 from electrical contact pads 48 formed on the surface of thetape head 2 which is opposite from the tape bearing surface 10.Electrical cables (not shown) may be attached to the contact pads 48using conventional techniques. Electrical connections to the readerelements 18 can be provided using conventional contact pads of the typeshown in FIG. 1, as are commonly used for vertical read elements.Although not shown, it would be possible to fabricate driver components,such as FETs (Field Effect Transistors), above the contact pads 48 ofthe write module 4. Alternatively, the drivers may be fabricated onseparate chips, which are then mounted close to the tape head 2. Thetape bearing surfaces 10 and 16 of the tape head 2 may be lapped todefine a preferred tape wrap angle as the tape “T” streams over thehead.

Turning now to FIGS. 11-14, an alternative write module 4′ is shown foruse in the tape head 2 in which the write elements 12′ comprise ahelical coil construction. According to this construction, the writecoil 20′ is constructed with plural coil windings in plural film layers“L,” as can be seen in FIG. 13. In particular, a first set of coilwinding elements 20A′ is formed in a first one of the layers “L,” asecond set of coil winding elements 20B′ is formed in a second one ofthe layers “L,” and third and fourth sets of coil winding elements 20C′and 20D′ (see FIG. 12) are formed in the intermediate layers that liebetween the coil winding elements 20A′ and 20B′. A pair of contact pads22′ and 24′ are provided for connecting the write coil 20′ to aninformation-modulated current source (not shown). The write elements 12′further comprise a pair of pole tips 26′ and 28′ that provide the writegap 14′ at the write module tape bearing surface 10′. A pair of polepieces 30′ and 32′ respectively extend from the pole tips 26′ and 28′ toa back gap region 34′ where the pole pieces are joined. The pole tips26′/28′ and the pole pieces 30′ and 32′ can be formed from any suitablemagnetically permeable material of the type conventionally used tofabricate inductive write heads for information storage. As can be seenin FIG. 13, the pole pieces 30′ and 32′ initially extend from the poletips 26′ and 28′ in a direction that is generally perpendicular to thewrite module tape bearing surface 10′. Each pole piece 30′ and 32′ thenmakes an approximate 90° bend at a separate one of the layers “L” of thewrite module 4′, and thereafter extends generally parallel to the writemodule tape bearing surface 10′ to the back gap region 34′. The back gapregion 34′ is thereby spaced in a trackwise direction from the write gap14′.

It will be seen in FIG. 13 that the write coil 20′ wraps around the polepiece 32′. When the write coil 20′ is energized, it will induce magneticflux in the pole pieces 30′ and 32′ so as to produce a magnetic field atthe pole tips 26′ and 28′ that propagates across the write gap 14′. Itwill be appreciated that the strength of the magnetic field at the writegap 14′ depends in part on the number of windings of the write coil 20′.The number of winding of the write coil 20′ can be increased byincreasing the length of the pole pieces 30′ and 32′.

Note that the helical configuration of the write coil 20′ allows thewrite elements 12′ to have a relatively narrow profile (as compared tothe pancake coil configuration described above) that facilitates reducedtrack pitch. As shown in FIG. 11A, the write elements 12′ may bearranged in one or more arrays. Plural arrays allow for a furtherreduction in track pitch. FIG. 14 shows the tape head 2 with thealternative write module 4′ when viewed from the edge of the tape “T” ofFIG. 11. The electrical connections to the write elements 12′ are thesame as described above in connection with FIG. 7.

Turning to FIG. 15, the inventive concepts herein described may beembodied in a tape drive data storage device (tape drive) 100 forstoring and retrieving data by a host data processing device 102, whichcould be a general purpose computer of other processing apparatusadapted for data exchange with the tape drive 100. The tape drive 100includes plural components providing a control and data transfer systemfor reading and writing host data on a magnetic tape medium. By way ofexample only, those components may conventionally include a channeladapter 104, a microprocessor controller 106, a data buffer 108, aread/write data flow circuit 110, a motion control system 112, and atape interface system 114 that includes a motor driver circuit 116 and aread/write head unit 118.

The microprocessor controller 106 provides overhead controlfunctionality for the operations of the tape drive 100. As isconventional, the functions performed by the microprocessor controller106 are programmable via microcode routines (not shown) according todesired tape drive operational characteristics. During data writeoperations (with all dataflow being reversed for data read operations),the microprocessor controller 106 activates the channel adapter 104 toperform the required host interface protocol for receiving aninformation data block. The channel adapter 104 communicates the datablock to the data buffer 108 that stores the data for subsequentread/write processing. The data buffer 108 in turn communicates the datablock received from the channel adapter 104 to the read/write dataflowcircuitry 110, which formats the device data into physically formatteddata that may be recorded on a magnetic tape medium. The read/writedataflow circuitry 110 is responsible for executing read/write datatransfer operations under the control of the microprocessor controller106. Formatted physical data from the read/write data flow circuitry 110is communicated to the tape interface system 114. The latter includesone or more read/write heads in the read/write head unit 118, and drivemotor components (not shown) for performing forward and reverse movementof a tape medium 120 mounted on a supply reel 122 and a take-up reel124. The drive components of the tape interface system 114 arecontrolled by the motion control system 112 and the motor driver circuit116 to execute such tape movements as forward and reverse recording andplayback, rewind and other tape motion functions. In addition, inmulti-track tape drive systems, the motion control system 112transversely positions the read/write heads relative to the direction oflongitudinal tape movement in order to record data in a plurality oftracks.

In most cases, as shown in FIG. 16, the tape medium 120 will be mountedin a cartridge 126 that is inserted in the tape drive 100 via a slot128. The tape cartridge 126 comprises a housing 130 containing themagnetic tape 120. The supply reel 122 is shown to be mounted in thehousing 130.

Accordingly, a planar write module and a hybrid planar write-verticalread bidirectional tape head comprising the write module and one or morevertical read modules have been disclosed. While various embodiments ofthe invention have been shown and described, it should be apparent thatmany variations and alternative embodiments could be implemented inaccordance with the teachings herein. It is understood, therefore, thatthe invention is not to be in any way limited except in accordance withthe spirit of the appended claims and their equivalents.

1. In a tape drive, a tape head for reading and writing data on amagnetic recording tape, comprising: a write module; a write module tapebearing surface on said write module for engaging said magneticrecording tape; plural write elements in said write module, each of saidwrite elements comprising plural thin film layers oriented in generallyparallel planar relationship with said write module tape bearingsurface; said write elements being arranged so that the transducing gapsof adjacent write elements are generally aligned in a direction that istransverse to a streaming direction of said magnetic recording tape; oneor more read modules; a read module tape bearing surface on each of saidread modules for engaging said magnetic recording tape; and plural readelements in said one or more read modules, each of said read elementscomprising plural thin film layers oriented in generally perpendicularrelationship with said read module tape bearing surface.
 2. A tape drivein accordance with claim 1 wherein said write module is disposed betweentwo read modules in a trackwise direction relative to said magneticrecording tape.
 3. A tape drive in accordance with claim 1 wherein saidwrite elements comprise a pancake coil construction.
 4. A tape drive inaccordance with claim 1 wherein said write elements comprise a helicalcoil construction.
 5. A tape drive in accordance with claim 1 whereinsaid write elements comprise a pair of pole tips providing a write gapat said write module tape bearing surface and a pair of pole piecesextending from said pole tips to a back gap region where said polepieces are joined, said back gap region being spaced in a trackwisedirection from said write gap.
 6. A tape drive in accordance with claim1 wherein said write elements are arranged with spaced write gaps.
 7. Atape drive in accordance with claim 1 wherein said write elements arearranged in one or more arrays.
 8. A tape drive in accordance with claim1 further including write channel circuitry for said write elementsfabricated in thin film layers of said write module.
 9. A tape drive inaccordance with claim 1 further including servo read elements on saidwrite module, each of said servo read elements comprising plural thinfilm layers oriented in parallel planar relationship with said writemodule tape bearing surface.
 10. A tape drive in accordance with claim 9wherein said servo read elements comprise a flux guide construction. 11.A write module for writing data on a magnetic recording tape,comprising: a write module tape bearing surface for engaging saidmagnetic recording tape; plural write elements in said write module,each of said write elements comprising plural thin film layers orientedin generally parallel planar relationship with said write module tapebearing surface; said write elements comprising a pancake coilconstruction with a pair of pole tips providing a write gap at saidwrite module tape bearing surface and a pair of pole pieces extendingfrom said pole tips to a back gap region where said pole pieces arejoined, said back gap region being spaced in a trackwise direction fromsaid write gap; and said write elements being arranged so that the writegaps of adjacent write elements are generally aligned in a directionthat is transverse to a streaming direction of said magnetic recordingtape.
 12. A write module in accordance with claim 11 wherein said writeelements are arranged in one or more arrays.
 13. A write module inaccordance with claim 12 wherein said write gaps are spaced byapproximately one gap width.
 14. A write module in accordance with claim11 further including servo read elements on said write module, each ofsaid servo read elements comprising plural thin film layers oriented inparallel planar relationship with said write module tape bearingsurface.
 15. A write module in accordance with claim 14 wherein saidservo read elements comprise a flux guide extending from said writemodule tape bearing surface to a sensor structure recessed from saidwrite module tape bearing surface.
 16. A write module for writing dataon a magnetic recording tape, comprising: a write module; a write moduletape bearing surface on said write module for engaging said magneticrecording tape; plural write elements in said write module, each of saidwrite elements comprising plural thin film layers oriented in generallyparallel planar relationship with said write module tape bearingsurface; said write elements comprising a helical coil construction witha pair of pole tips providing a write gap at said write module tapebearing surface and a pair of pole pieces extending from said pole tipsto a back gap region where said pole pieces are joined, said back gapregion being spaced in a trackwise direction from said write gap; andsaid write elements being arranged so that the write gaps of adjacentwrite elements are generally aligned in a direction that is transverseto a streaming direction of said magnetic recording tape.
 17. A writemodule in accordance with claim 16 wherein said write elements arearranged with spaced write gaps.
 18. A write module in accordance withclaim 16 wherein said write elements are arranged in one or more arrays.19. A write module in accordance with claim 16 further including servoread elements on said write module, each of said servo read elementscomprising plural thin film layers oriented in parallel planarrelationship with said write module tape bearing surface.
 20. A writemodule in accordance with claim 19 wherein said servo read elementscomprise a flux guide extending from said write module tape bearingsurface to a sensor structure recessed from said write module tapebearing surface.